Donley, who’s led the Air Force during the past five years, is retiring after 35 years of public service.

“Our country will miss him,” Hagel said of Donley.

Hagel was accompanied by Deputy Defense Secretary Ash Carter at the event, where hundreds gathered to say farewell to Donley.

The defense secretary said Donley’s leadership as the Air Force’s top civilian rested on hard work, constant attention, and the trust and confidence of his subordinates.

Donley understood that the nation’s defense is “a team business,” Hagel said.

“If we had more of the Mike Donley attitude and sense of purpose in our country today, we’d probably all be a little better off,” Hagel said. “ … I have been impressed [and] inspired. He has never shied away from taking the big issues on, straight up.”

Donley thanked his family, friends and colleagues for their support throughout his career.

“Above everything else, I’m most grateful to have had this opportunity to meet, to know, and to represent America’s airmen,” he said.

Through interaction with those airmen, Donley said he’s witnessed how service changes lives.

“Trust, confidence and respect are part of our Air Force heritage … they must never be taken for granted,” Donley said.

Air Force Chief of Staff Gen. Mark A. Welsh III said in remarks that Donley led efforts from reinvigorating the Air Force’s nuclear enterprise to modernizing the force by overseeing the successful award of the KC-46 tanker contract, initiating work on the long-range strike family of systems, and guiding the F-35 joint strike aircraft program “through some turbulent times.”

Carter credited Donley with rebuilding the morale and reputation of the Air Force, “brick by brick.”

The deputy defense secretary also described Donley as a man of great integrity and humility.

“You have left behind a lasting achievement, for which you have our lasting gratitude,” Carter told Donley.

Before taking the oath as Air Force secretary in October 2008, Donley was director of Administration and Management for the Office of the Secretary of Defense. He has also served on the Senate and White House staffs and worked in private industry, and is an Army veteran.

Eric Fanning, undersecretary of the Air Force, will serve as acting secretary until Donley’s replacement is confirmed.